The broad, long term objective of the proposed research is the development of Optical Doppler Tomography (ODT) for application in the clinical management of patients with PWS by providing a semi-quantitative evaluation of the efficiency of pulsed laser therapy. If partial replenishment of flow occurs immediately or shortly after pulsed laser exposure, indicative or reperfusion due to in inadequate blood vessel injury, the PWS can be retreated. This process is continued until the measured Doppler shift is zero due to a permanent reduction in blood flow after laser exposure, indicative of irreversible microthrombus formation in the PWS vessels. The specific aims of this proposal are to 1)determine the importance of Doppler shift, scattering and absorption on the ODT signal amplitude and frequency; 2) apply ODT to characterize blood flow at discrete spatial locations in either the superficial or deep skin microcirculation in preclinical animal model representative of PW S; and 3) demonstrate the practical application of the technique to the clinical management of patients with PWS undergoing laser therapy.